Business Math
posted by Thank you .
A $20,000 loan is amortized by equal semiannual payments over 10 years. If the interest rate is 8% compounded semi annually find the size of the payments. What is the unpaid balance after 6 years? Prepare the amortization schedule for the 1st 3 periods and find the principle repaid in the 2nd payment.

I think the payment is: 20k= PMTx1/.04 *(1(1/(1+.04)20)
PMT = 1471.63

I think the amortization table looks like:
Time:Payment: Interest: Repaid: Balance
0: 0: 0: 0: 20k
1:1471.63: 800: 671.64: 19328.36
2:1471.63: 773.13: 698.51: 18629.85
3:1471.63: 745.19: 726.45: 17903.40
Principle= 20k18629.85=1370.15

Is there a formula I can use for
What is the unpaid balance after 6 years?

I've been looking on google and the duck but can't seem to find anything that helps my brain understand finding the balance. I have a test tomorrow any any help would be greatly appreciated.